1. Field of the Invention
The present invention generally relates to manufacturing methods of magnetic recording media, the magnetic recording media, and magnetic recording and reproducing apparatuses. More specifically, the present invention relates to a manufacturing method of a magnetic recording medium whereby a magnetic pattern is formed by ion implantation, the magnetic recording medium, and a magnetic recording and reproducing apparatus.
2. Description of the Related Art
Hard disk drives (HDD) are mainly used as mass storage devices whereby high speed access or high speed transmitting of data can be realized. The surface recording density of the hard disk drives (HDD) is being improved at an annual rate of 100% and further improvement of recording densities is expected.
In order to improve the recording densities of the HDDs, reduction of the track width or the recording bit length is necessary. However, if the track width is reduced, neighboring tracks may easily interfere with each other. Due to such a reduction of the track width, the magnetic recording information may be easily overwritten in the neighboring tracks at the time of recording. Cross-talk due to leakage magnetic fields from the neighboring tracks may easily occur at the time of reproducing.
The above-mentioned problems cause reduction of the S/N ratio of a reproduction signal so that the error rate may be degraded. In addition, if the reducing the recording bit length is continued, stability of the bit becomes degraded and the phenomenon of heat fluctuation is generated.
On the other hand, in a case of perpendicular magnetic recording, magnetizations of neighboring bits of a disk medium do not face each other and the bits are strengthened. The perpendicular magnetic recording is advantageous for high density recording in principle compared to longitudinal magnetic recording where magnetizations of neighboring bits face to each other. Hence, a lot of companies have started conversion to a perpendicular magnetic recording type.
However, in a perpendicular magnetic recording type where conventional continuous media are used, it is difficult to realize extra high density recording equal to or greater than 1 Tbpsi. Because of this, a bit pattern medium (hereinafter “BPM”) is attractive as a way for realizing the extra high density recording. In the BPM, a medium recording film is processed so that a bit pattern is formed on the disk in advance.
However, in a forming method of the magnetic recording medium by the BPM, a portion other than the bit pattern is etched so that the magnetic film is removed and then a non-magnetic material is supplied and flattened to fill in that portion. Hence, it is necessary to perform complex manufacturing processes so that the manufacturing cost may increase.
As a method for solving such a problem, a processing method whereby ions are implanted into a magnetic film so that a magnetic state is partially changed has been suggested. See Japanese Laid-Open Patent Application Publication No. 2005-228912. In this method, since the magnetic state is changed by implanting the ions, a complex manufacturing process such as etching, filling or flattening is not required so that increase of the manufacturing cost is prevented.
As a manufacturing method of the BPM by the ion implantation in the conventional art, a method has been used where, for example, ion implantation is partially performed on a FePt magnetic film having a CuAuI type ordered structure with high magnetic anisotropy so that a low coercive force is achieved. In this conventional method, an area where ion implantation is performed is treated as a magnetic recording impossible area (isolated area) and an area where ion implantation is not performed is treated as a magnetic recording possible area.
As discussed above, in the conventional manufacturing method of the BPM, a magnetic recordable material is selected as a magnetic film formed on a substrate, and ion implantation is performed on a portion other than the recording area layer so that the isolation layer is formed; thereby a recording area and an isolation area are formed in the same magnetic film.
However, in the conventional manufacturing method of the BPM, the magnetic properties of the recording area are the same as the magnetic properties of the magnetic film formed on the substrate so that it is difficult to improve the magnetic properties.